1. Field of the Invention
The present invention relates to a measurement device such as a rangefinder to measure the distance to an object and a focus detection device to detect a focus condition of a taking lens, for use in cameras, video cameras and the like.
2. Description of the Related Art
Phase difference detection methods are known to be used as measurement device, rangefideres and focus detection devices, in cameras and the like to measure the distance to an object.
Such rangefinders, for example, are provided with a pair of photoelectric conversion elements (line sensors) as a standard unit (left sensor) and reference unit (right sensor), and further provided with a left memory and right memory having a storage capacities corresponding to the number of elements, i.e., number of pixels, of the left sensors and right sensors.
In the aforesaid construction, an object image (distance information) obtained by photoreception via the left sensor and right sensor is stored in the respective memories as pixel data, then blocks are divided into a plurality of regions in accordance with the obtained pixel data array, and thereafter calculations are executed to determine the correlation value relative to the pixel data between the left sensor and right sensor for each the block, distance data are calculated which correspond to the distance to the measurement object using a plurality of obtained correlation values.
In the aforesaid conventional rangefinder, since photoreception of measurement information of an object is required over a broad measurement range in order to improve measuring precision by increasing the amount of measurement information, a plurality of photoelectric conversion elements are used in the left sensor and right sensor. Therefore, as the number of photoelectric conversion elements increases the storage capacity of the left and right memories must be correspondingly increased, thereby exacerbating the tendency of increasing memory capacity. On the other hand, if memory capacity is restricted, a disadvantage arises insofar as the extension area of the measurement range is limited so as to produce a fixed boundary on precision.